Q345 steel pipe

Brief Introduction Of Low Alloy High Strength Steel 16Mn

Many steel material buyers purchase steel plate in China, especially high strength low alloy steel. 16Mn is kind of C-Mn steel, its carbon content is from 0.1% to 0.25% and with some alloy elements such as manganese (Mn), silicon (Si), vanadium (V), niobium (Nb), titanium (Ti) and other elements. 16 Mn is a kind of low alloy steel with large output and the most extensive application. This kind of steel can be used as the alternative material of many kinds of steel.Today we introduce 16Mn as your reference for purchasing steel plate in China.

As a old Chinese standards, 16Mn is edited from GB 1591-1988 “low alloy structural steel”, has now been replaced by Q345. Low alloy steel Q345 steel has 5 quality grades, which are represented by from  Q345A to Q345E. It can be said that Q345 steel is the substitution of old brand steel of 12MnV, 14MnNb, 18Nb, 16MnRE, 16Mn and other steel types, rather than only 16Mn steel. Their corresponding foreign maters are showed below:

Q345AGrade 50SPFC 590 E335(St 52-3)1.0060
Q345BGrade 50SPFC 590S355JR 1.0045
Q345CGrade 50SPFC 590S355JO1.0553
Q345DGrade 50SPFC 590S355J21.0577
Q345EGrade 50SPFC 590S355NL1.0546

What’s The Difference Between 16Mn And Q345?

The chemical element of Q345 steel is basically the same as that of 16Mn steel. The difference lies in the addition of Ti, Nb and V micro alloying elements, which can refine grain, improve toughness, and finally improve the mechanical properties of steel. In other words, the comprehensive mechanical properties of Q345 steel are better than that of 16Mn steel, especially its low temperature performance and allowable stress.

Standards comparison

16MnGB 28883-2012 Composite seamless steel pipe for pressure applicationNB/T 47008-2010 Carbon steel and alloy steel forgings for pressure equipmentGB 6479-2000 Seamless steel pipe for high pressure fertilizer equipmentGB 1591-1988 Low alloy structural steel
Q345GB/T 1591-2008Low alloy and high strength structural steel

Chemical composition comparison


16Mn is a typical grade of low alloy high strength steel, mainly including 16Mn steel plate, 16Mn seamless tube and 16Mn forgings, they are widely used in the manufacture of medium and low pressure vessels and oil tanks as well as general mechanical structural parts.

The ratio of the main constituent elements of Q345 steel is basically the same as that of 16Mn steel. The difference is the addition of Ti, Nb, and V trace alloying elements.

Q345 steel is the replacement of the old grades of 14MnNb, 12MnV, 16MnRE, 16Mn, 18Nb, and other steels, not just the replacement of 16Mn. In terms of chemical composition, 16Mn and Q345 are also different. More importantly, there is a big difference in the thickness grouping size of the two steel materials according to the different yield strength, which will inevitably cause the change of the allowable stress of certain thickness materials. Therefore, it is not appropriate to simply apply the allowable stress of 16Mn steel to Q345 steel, and the allowable stress should be re-determined according to the new steel thickness grouping size.

The ratio of the main constituent elements of Q345 steel is basically the same as that of 16Mn steel. The difference is the addition of Ti, Nb, and V trace alloying elements. A small amount of Ti, V, and Nb alloy elements can refine the grains, improve the toughness of the steel, and greatly improve the comprehensive mechanical properties of the steel. Because of this, the thickness of the steel plate can be made larger. Therefore, the comprehensive mechanical properties of Q345 steel should be better than 16Mn steel, especially its low temperature performance is not available in 16Mn steel. The allowable stress of Q345 steel is slightly higher than that of 16Mn steel.

Q345 Steel | Equivalent Materials & Metal Specifications

Q345 is a low alloy steel material commonly used in motor vehicles, bridges, ships, and construction. Also known as GB/T 1591, the Q signifies the yield point, and the 345 references the strength of yield. As such, it is essential to note that the yield value decreases as the material thickness increases.

Q345 Equivalent Materials

Q345 can also be replaced with equivalent materials, including A572 Grade 50 USA ASTM, Q355 China GB/T, and SPFC 590 Vietnam/Japanese JIS.

Characteristics of Q345

The yield strength of Q345 is where the material begins to deform plastically. Before hitting deformation, it will return to its original shape when stress is removed. For Q345, the yield strength is 345 MPa.

Like many in its grade, it will endure elongation before pulling apart, which typically occurs at 20 percent of its initial length. Q345 has a tensile strength rating of 470 to 660 MPa, which means that it can handle heavy-duty stress and use before ever failing.

The welding property of Q345 may be questioned by end-users, even though the welding properties are primarily affected by the chemical content. However, the production technology has rapidly and significantly improved after many years of research, which means that it is an excellent steel standard for structural purposes.

Q345 steel is from the 16 Mn steel grade, typically manufactured in a hot rolled steel coil or sheet or a hot rolled steel plate. It is an excellent choice when you need high-pressure durability.

Uses of Q345

Q345 has excellent mechanical properties, good performance in low temperatures, and excellent weldability and plasticity. It is most commonly used in building structures, low-pressure vessels, cranes, mechanical parts, bridges, ships, petroleum storage tanks, lifting machinery, power stations, mining machinery, general metal parts, and in other structures that are exposed to temperatures of -40 ℃ or below or experience high-loads.

Q345 Physical Properties

Physical PropertiesMetricUS/Imperial
Density7.80 g/cc0.282 lb/in³

Q345 Mechanical Properties

Mechanical PropertiesMetricUS/Imperial
Hardness, Brinell135135
Hardness, Rockwell B7474
Tensile Strength, Ultimate450 MPa
Tensile Strength, Yield345 MPa
Elongation at Break18 %18 %
21 %21 %
Bulk Modulus160 GPa23200 ksi
Shear Modulus80.0 GPa11600 ksi

Q345 Component Elements Properties

Component Elements PropertiesMetricUS/Imperial
Carbon, C<= 0.23 %<= 0.23 %
Iron, Fe98 %98 %
Manganese, Mn1.35 %1.35 %
Phosphorus, P<= 0.040 %<= 0.040 %
Silicon, Si<= 0.40 %<= 0.40 %
Sulfur, S<= 0.050 %<= 0.050 %
Silicon, Si0.15 – 0.40 %0.15 – 0.40 %
Sulfur, S0.050 %0.050 %

*Redstone Manufacturing does not guarantee the accuracy of the information contained within the above table. 

Formability and Weldability

The major benefit of this grade of steel is its mild temper. It’s easy to form and easy to weld, allowing it to be used to put sheet plate on doors, steel cabinets and the exterior surfaces of most objects. Chances are, if you’ve got an object with a steel exterior that was made in China, this is the grade of steel used for the outside of it. It is the combination of comparatively low price and ease of use that makes this steel nearly ubiquitous in consumer goods where low weight isn’t a major concern.

Q345 steel plate

What is the difference between Q345 material and 16Mn steel

Q345 material and 16Mn steel are a kind of steel names. Their starting points are different. Q345 material is named from the yield strength of steel, Q stands for yield strength (initial letter of yield), 345 is the value of yield strength, which is 345 Mpa. However, 16Mn steel refers to 0.16% carbon content and 0.7% – 1.0% manganese content.

In addition, the name of 16Mn steel is the old national standard, that is, the former name, because the former national standard has requirements on the manganese content of this material, that is, the manganese content is between 0.7% – 1.0%. However, the new national standard does not require the manganese content of this material, so it does not need to be expressed in 16Mn steel, which is replaced by Q345 material.

Usually, I have friends who ask 16Mn steel, and I will explain to him. Of course, if there are certain requirements for manganese content of Q345 material, I will also screen for customers and try to meet his requirements.

  1. Classification by quality grade: Q345 is low-alloy steel of ordinary quality, and 16Mn is high-quality low-alloy steel.

Q345 belongs to GB/T1591-94 low-alloy high-strength structural steel. 16Mn belongs to JB4726-2000 carbon steel low alloy steel forgings for pressure vessels. Looking at the standards, it should be clear that the two steels have different uses.

In comparison, 16Mn has stricter requirements for sulfur and phosphorus content, and stricter quality requirements. 16MN and Q345 are the same in general use, but only 16MN can be used for containers and boilers, because Q345 is not listed in GB150, if you want to use it, the procedure is very troublesome, and it is classified according to characteristics. Both are weldable low alloy high strength structural steel.

  1. The starting point of the name is different

Q345 and 16Mn are a name for steel. Their starting points are different. Q345 is named from the yield strength of steel. Q stands for yield strength (the first letter of yield), and 345 is the value of yield strength. And 16mn refers to the carbon content of 0.16%, manganese content (0.7%-1.0%).

The name of 16mn is the old name of the national standard, that is, the previous name, because the previous national standard has requirements for the manganese content of this material, that is, the manganese content is between (0.7%-1.0%), and the new national standard has already There is no requirement for the manganese content of this material, so 16mn is not used to represent it, and q345 is used instead.

What material is equivalent to 16Mn?

The ratio of the main constituent elements of Q345 steel is basically the same as that of 16Mn steel.

GB 16Mn low-alloy steel Chemical Composition:

Grade C% max Si% max Mn% max P% max S% max
16Mn 0.12-0.20 0.20-0.55 1.20-1.60 <=0.045 <=0.045

Mechanical Properties of 16Mn

Tesile ób/Mpa470-660
Yield ós/Mpa(min)275-345
Elongation δ5(%)(min)21
SAFA Aku/J(min)
Brinel hardness HBS(max)
16mn steel pipe 03

16Mn Steel is a carbon-manganese steel, carbon content of 0.16%, the yield point is equal to 343MPa (strength level belonging to 343MPa). Less the 16Mn steel alloy content, good weldability, and generally do not have to warm-up before welding.Its total alloy content is less than 3%. According to the strength, it is divided into 4 levels of 300, 350, 400 and 450MPa. There are mainly Q235, Q345, Q390, Q420, Q460. : “Q” is the initial Chinese pinyin of the word “qu” for yielding, the following number is the minimum yield point (σs) value of the grade, and the following symbol is based on the increase in the content of impurity elements (sulfur, phosphorus) of the steel It is divided into four grades A, B, C, D when it is low and with the change of carbon and manganese elements. Among them, A and B grade steels are usually called 16Mn.

16Mn is a material in steel. A name for steel material.

16Mn steel belongs to carbon-manganese steel, the carbon content is about 0.16%, and the yield point is equal to 343MPa (strength grade belongs to 343MPa grade). 16Mn steel has less alloy content and good weldability. Generally, it is not necessary to preheat before welding . However, because the hardening tendency of 16Mn steel is slightly greater than that of low-carbon steel, preheating measures must be taken to prevent cold cracks when welding at low temperatures (such as outdoor operations in winter) or on large rigid and large thickness structures .